Components such as high performance electrical connectors typically have one or more sets of cylindrical shells which mate with recesses when male and female parts are joined. Means for focussed visual inspection with ambient light of the recesses are necessary to, for example, verify the operative status of contacts inside them. Manipulation of parts in or near the recesses may also be desired during inspection. These features have not previously been provided by known instruments for viewing the internal surfaces. For example, in Alsberg, U.S. Pat. No. 4,072,427, an inspection system is described using a cylinder having a separate lens and mirror system and requiring a specific source of illumination. Similarly, in Troeo, U.S. Pat. No. 3,413,067 and Jones, U.S. Pat. Nos. 4,135,824 and 3,724,922, rod like endoscopes are provided for viewing internal surfaces. None of these, however, provide an annular instrument capable of insertion in a cylindrical recess which has magnifying power, provides a clear in-focus view of the entire internal cylindrical surface simultaneously, and uses ambient external light for illumination.